Etching device for rotogravure cylinders



April-30, 1946. I Q ALGER 2,399,534

ING DE E Filed Jan. 29, 1945 2 Sheets-Sheet 1 April 30 1946. H; c. ALGER2,399,534

ETCHING DEVICE FOR ROTOGRAVURE CYLINDERS Filed Jan. 29, 1943 2Sheets-Sheet 2 Patented Apr. 30, 1946 UNITED STATES PATENT OFFICEETCHING DEVICE FOR ROTOGRAVURE CYLINDERS 9 Claims.

This invention relates to the art of etching rotogravure printingcylinders and more particularly to the so-called tank or trough methodof etching wherein the cylinder to be etched is revolved in a troughpartly filled with a suitable etching device or apparatus and a methodof procedure which will enable the etcher to standardize and produceuniform results so that it will be unnecessary to etch cylinders overagain as is now often the case; another object is to simplify theprocedure of etching; another object is to produce a device which willenable the etcher to etch all parts of a cylinder equally which willreduce the necessity for reetching parts of the cylinder now often thecase; while still another object is to provide a method of etching whichwill conserve the mordant.

Other objects will be evident from the following description:

Rotogravure printing cylinders are commonly prepared for etching byproviding a cylinder having a polished copper surface, mounted on ashaft having journals or trunnions extending axially from each end ofthe cylinder and mounting this cylinder on a suitable truck, stand orother support with the journals held in bearings and with at least oneend of the shaft extending and carrying a wheel or a suitable connectionfor a motor by means of which one may easily revolve the cylinder aboutits axis during the preparatory and etching operations.

Next a sheet of sensitized gelatin coated paper commonly called carbontissue is screened and printed by light through a positive transparencycarrying the desired image, the carbon tissue is laid down on thesurface of the cylinder, the paper is soaked with warm water until it isreadily removed and the gelatin remaining on the cylinder is developedby further washing with warm water leaving the image carrying gelatin onthe cylinder in the form of a resist of variable thickness, that is, thegelatin carrying the image is thin in the tones corresponding with thedark tones of the positive and relatively thick in the tonescorresponding with the light tones of the positive, with intermediatetones in proportion. The gelatin is then dried and the margins betweenimage bearing portions of the cylinder and other non-image portions ofthe cylinder are painted over with asphaltum commonly called staging sothat these portions will not be affected by the mordant and the cylinderis thus made ready for etching.

At present, the common method of etching is to mount the cylinder,prepared as previously described, in a horizontal position, over a sinkadapted to collect the mordant as it drips from the cylinder and withthe ends of the shafts which extend from the cylinder resting inbearings on a suitable truck or stand. The cylinder is then revolvedeither by means of a hand wheel attached to one end of the shaft or by amotor which may be connected to the shaft by a suitable gear arrangementso as to revolve the cylinder slowly, in the bearings. The mordant whichis iron perchloride is then either poured over the cylinder or isapplied by dipping cotton into a pitcher of the mordant and swabbing iton by hand and rubbing the cylinder lightly as it revolved so as toapply the mordant more or less evenly over the cylinder.

I have found that when pouring the mordant over the cylinder, it tendsto run in uneven streaks around the cylinder, thus tending to produceuneven etching, and while swabbing or rubbing the cylinder with themordant tends to smooth out this unevenness to some extent, the rubbingitself injects another variable into the etching process. First, suchswabbing or rubbing may produce streaks in the etching in the directionin which the cylinder is rubbed because of uneven application of themordant over various parts of the cylinder, and second, since there isno good way to always swab or rub in an exact manner so that all partswill receive exact and equal treatment, there is apt to be, not onlyvariation in the etching of one part of the cylinder as compared withsome other part, but also a variation between cylinders as there is noway to standardize the etching of different cylinders. More rubbingtends to hasten the action of etching while less rubbing tends to reducesuch action,

It is not possible to produce the best results in etching b the use of asingle strength of the mordant which is iron perchloride, commonlycalled iron. It is quite common to have five or six different dilutionsof the iron perchloride from one reading about 44 Beaume' down to 39 or38 Beaum already prepared and then to change to each of the lowerreading dilutions as the etching progresses. Moreover it is common tostart with 44 iron and change to say 42 iron to get the etching started;then change back to 44 or 43 iron to slow down the etching so as to gettone separation, subsequently .it terminates in a handle [5.

proceeding to use each of the lower dilutions in turn until the etchingis completed, it being necessary to complete the etching about twominutes after the lightest tone starts to etch, while at the same time,the darkest tones must be completed without etching so far as to etchaway the walls or the screen lines in these tones.

It will be evident that when making these changes, it will be of greathelp to make them quickly without delay whenever such a change isdecided upon.

Methods of etching wherein the cylinder to be etched is revolved in themordant held in a trough or tank have been largely abandoned becauseheretofore no way has been devised to empty the tank quickly and makethe change quickly, and no way has heretofore been devised to insureuniformity in the etching action.

In my invention, it will be seen that I have produced an etching deviceand a method of using it whereby these diificulties are almost entirelyremoved, where the trough may be drained very quickly without the use ofcumbersome valves, and new mordant applied quickly and where the actionof rubbing is replaced by a surging action of the mordant itself whichmay be accomplished in a uniform standardized. manner over the surfaceof each cylinder and also over each and every cylinder.

In the accompanying drawings:

Fig. 1 shows a perspective view of my improved etching device mounted onthe shafts of a cylinder which cylinder is supported with its shafts inbearings on an etching stand or truck ready to be Wheeled over to a sinkfor the purpose of etching;

Fig. 2 shows an end view of the device in position over a sink, a pairof rollers of the truck bearing being shown supporting the cylindershaft but with truck removed;

'Fig. 3 shows an end view of the device as it may be lowered away fromthe cylinder during the operation of washing;

Fig. 4 shows a detail of the latch which holds the trough in either itsetching or washing position;

Fig. 5 shows a modification of my invention in which a very simplyconstructed etching trough is used.

In Fig. 1 a conventional cylinder truck or stand I is shown supportingthe cylinder 2, with its shafts or trunnions 3 and 4 resting in bearings5 and 6 forming parts of the truck.

The truck is carried by swivel castors 1 which facilitate movement ofthe cylinder through its various operations. The truck may be moved tohold the cylinder over a sink 8, in Fig. 2 where shaft 3 is shownsupported by two rollers C and D, parts of bearing 5. A drain pipe 28 isadapted to drain from the sink any liquid collected therein. A handwheel 9 attached to one of the shafts may be used to revolve thecylinder in either direction. The etching trough Ill is normally heldwith its concave bottom in close proximity to the lower portion of thecylinder as shown in Fig. 2, this clearance dimension beingapproximately 1%" to /8. It is carried by two clamping devices A and Bin Fig. 1, at either end of the cylinder, the clamping device A beingshown more in detail in Fig.

Each clamping device comprises a pair of arms II and I2 hinged at l3.Arm H is curved to pass above the cylinder shaft 3 to the opposite sideof the cylinder where it terminates in a knob l4. Arm I2 is curved topass under the cylinder shaft 3, also to the opposite side of thecylinder where A hearing .block 16 is fastened to arm II by adjustingscrews I! and 58 which permit adjusting the block to its desiredposition by virtue of slots l9 and 20. The block it is made in aninverted U-shape to fit the shaft and is held from up and down motion bya bar 21 secured across the open end of the block in any preferredmanner. The arm I2 is riveted or secured to the end of the trough ID asshown. A double latch 22 is secured to arm I2 near its handle end l5. Bytaking hold of knob M of arm I l and springing the arm, it may besnapped into position shown in Fig. 2 with arm I l between two prongs 23and 24 of the latch as shown in Fig. or it may be placed in contact withprong 25 with the arm l2 swung down to support the trough in a loweredposition as shown in Fig. 3. It is to be understood that the secondclamping device 3 of Fig. 1 is of similar construction and carries theother end of the trough.

In my preferred form of trough, the main body portion is concave with apouch portion or pro tub'erance at one side as shown at 26. This pouchor belly is adapted to hold the mordant out of contact with the cylinderduring the operation of diluting the mordant when the trough is turnedwith the pouch at its low point as will be more fully described, whileat the same time permitting swinging of the trough with its handle andknob to a vertical position when the mordant will quickly drain from thetrough into the sink. A stop 21 which engages with one of the arms llmay be used to hold the trough in its level position and prevent it fromturning in one direction, the weight of the arms of the clamping devicebeing sufiicient to prevent turning in the opposite direction.

In .the simplified form shown diagrammatically in Fig. 5, the trough 29is shown as being concave in cross section without a pouch, but it stillhas the feature of quick draining and holding the bottom close to thelower portion of the cylinder to produce the surging action of themordant which eliminates the necessity for rubbing the cylinder duringetching and standardizes this operation. This form is of particular usewhere it is desired to hold each mixture of mordant in condition asoriginally mixed in one method of etching as will be more fullydescribed. I

In actual use of the preferred form of my invention as shown, there arethree methods that may be employed: In the first method, a supply ofiron perchloride is prepared in about six different dilutions of five tosix litres each, reading approximately 44 down to 39 Beaum inclusive,which may be referred to as Nos. 1 to 6 inclusive, for convenience. Thecylinder is then supported on the stand or truck and the etching troughis secured in position as shown in Fig. 2 and the stand is moved intoposition to support the cylinder with the trough over the sink. Thecylinder is then revolved usually by hand at a peripheral speed of aboutto 200 lineal feet per minute and the N0. 1 iron is poured over thecylinder and is caught in the trough and keeps the cylinder covered allover its surface with the iron. During this first application of iron tothe cylinder, it is advisable to wipe the iron lightly over the surfaceof the cylinder with cotton to free any air fro-m its surface and toinsure that the surface is wetted evenly all over. This operation is notto be confused with rubbing during etching because the cylinder will notstart to etch for some little time. The cylinder should preferably berevolved in one direction for about one minute and then reversed torevolve in the opposite direction for an equal time, reversing eachminute to keep the action uniform.

After the etcher decides that the No. 1 iron has performed its purpose,he swings the trough about the cylinder axis by lifting on the handlesso as to spill all the iron from the trough into the sink, then heswings the trough back to its first position and pours the next ironwanted, perhaps No. 2, over the cylinder or into the trough, thuscontinuing the etching with this iron with.- in an elapsed time of eightor ten seconds. In the meantime, the No. 1 iron is collected in the sinkand passes through the drain to a suitable receptacle, not shown, whichmay tak a minute or so.

In like manner, the etcher continues using the difierent solutions ofiron as desired until the etching is completed, when he swings thetrough and spills the last iron into the sink, he then swings the troughback and moves the knob arm H from the lower latch and swings the arm l2down until the arm ll engages with the upper latch so that the troughdrops to position as shown in Fig. 3. He can then apply wash waterquickly to the cylinder to stop the etching action and the water will becaught in the trough out of contact with cylinder and be held thereuntil the last iron is drained from the sink, when the trough may beswung to drain the wash water to the sink. The trough is then unlatchedand removed from the cylinder and the truck may be moved away with theetched cylinder.

One of the primary features of this method is that lower portion of thecylinder is very close to the bottom of the trough and the ends of thetrough should be quite close to the ends of the cylinder so thatrevolving the cylinder rather rapidly produces a sort of pumping actionwith the iron, causing it to rise on the side of the cylinder in thedirection which the cylinder is passing through the iron and thusproducing a pressure or head of iron on this side, causing surging ofthe iron against the cylinder and a rushing back in the confined spaceunderneath the cylinder. This action gives even agitation throughout thelength of the cylinder and eliminates necessity of rubbing the cylindermanually while etching. It will be evident that this agitation action isquite constant for any given speed so that it may be standardized toproduce uniform results.

The second method of using the device enables the etcher to produce manychanges of iron thus smoothing out the etching action by the simplemethod of providing two pitchers of iron, applying the first pitcher,then adding a slight amount of water to the second pitcher, say enoughto bring it to a Beaum reading of 43%, allowing the first iron to etchsay 1 /2 minutes, then quickly spilling the iron into the sink andchanging to the second iron, allowing this to etch about 1% minutes, inthe meantime adding enough water to the first iron to bring it to aBeaum reading of say B changing to etch with this iron and by keepingdiluting alternate pitchers of iron and changing at one orone-andone-half minute intervals, to apply fifteen or twenty diiferentstrengths of iron during a twenty-five minute etch. The simple form ofmy invention as shown in Fig, 5 may be used in the two methods justdescribed equally well with this form shown in Fig. 2.

In the third method, the form shown in Fig. 2 only is used which may beused equally well with the first two methods also.

In the third method, a result similar to that of method two may beobtained by the use of one pitcher of iron only, the amount being about5 or 6 litres in etching a newspaper size cylinder. In this method, theiron say 44 Beaum is poured over the cylinder and the etching is startedas before. After about one minute, the trough is swung so as to throwthe pouch to its lowest position. The iron runs into the pouch out ofcontact with the cylinder, a previously planned amount of water is addedby pouring along the length of the cylinder and stirred well into theiron, the trough is then swung back to its original position, thisoperation taking only 12 to 15 seconds and the cylinder is allowed toetch one minute to 1 /2 minutes when a change is made again in the samemanner just described. In this way, the etching can be smoothed out withmany changes of iron using only the small amount measured out to startwith, thus saving iron.

Having thus described my invention, what I claim is:

1. A device for etching a rotogravure printing cylinder, comprising astand for supporting the cylinder in a horizontal position so that itmay be revolved about its axis, and an etching trough adapted to hold amordant in contact with a portion of the cylinder during the operationof etching, means for supporting said trough so that it may be swungabout the axis of the cylinder whereby the mordant is quickly drainedfrom the trough.

2. A device for etching a rotogravure printing cylinder, comprising astand upon which the cylinder to be etched may be revolubly mounted withits axis horizontal and a trough adapted to hold a mordant in contactwith a portion of the cylinder during the operation of etching,swingingly supported under the cylinder so that it may be swung about anaxis substantially coaxial with the axis of the cylinder whereby themordant may be quickly drained from the trough. 3. In a device foretching a rotogravure printing cylinder, a stand upon which a cylindermay be revolvably mounted, and a trough shaped to hold an etchingmordant in contact with a portion of the cylinder and adapted to swingabout an axis substantially coaxial with the axis of the cylinderwhereby the mordant may be quickly drained from the trough.

4. In a device for etching a rotogravure printing cylinder a sink, meansfor supporting a cylinder over the sink and a, trough adapted to hold amordant in contact with a portion of the cylinder during the operationof etching, means for supporting said trough so that it may be swungabout an axis substantially on the center line of the axis of thecylinder whereby the mordant is quickly drained from the trough into thesink.

5. In a device for etching a rotogravure printing cylinder a sink, meansfor supporting a cylinder over the sink, a trough adapted to hold amordant in contact with a portion of the cylinder during the operationof etching, means for supporting said trough so that it may be swungabout an axis substantially on the center line of the axis of thecylinder whereby the mordant is quickly drained from the trough into thesink, and means for lowering the trough whereby wash water applied tothe cylinder may drip into the trough and be held in the trough withouttouching the cylinder.

6. In a device for etching a rotogravure printing cylinder, a sink, astand for supporting a cylinder over the sink in a horizontal positionso that it may be revolved about its axis, a trough adapted to hold amordant in contact with the cylinder during the operation of etching,mounted between the cylinder and the sink in a swinging position wherebythe trough may be swung about an axis substantially in line with theaxis of the cylinder thereby causing the mordant to be quickly drainedfrom the trough into the sink and means for lowering the trough awayfrom the cylinder whereby the trough may receive any wash water whichmay be applied to the cylinder and retain the wash water out of contactwith the cylinder.

7. A device for etching a rotogravure printing cylinder, comprising astand for supporting the cylinder in a horizontal position so that itmay be revolved about its axis and an etching trough adapted to hold amordant in contact with the lower portion of the cylinder during theoperation of etching, said trough being positioned with 20 volvedthrough the mordant, with a consequent 25 surging of the mordant againstthe cylinder, said trough being mounted so that it may be swung about anaxis substantially in line with the axis of the cylinder whereby themordant may be quickly drained from the trough.

8. In an apparatus for use in etching cylinders, the combination of areceptacle adapted to receive the lower portion of the cylinder and tofit closely against the ends thereof, the receptacle having a generallyconcave transversely arcuate bottom of larger diameter than the diameterof the cylinder, means for rotatively supporting the receptacle on thecylinder, and means for adjusting the receptacle toward and away fromthe cylinder, the arrangement being such that the receptacle may beswung to quickly empty the same for the purposes described.

9. In an apparatus of the character set forth for etching a printingcylinder, a pan having a transversely curved bottom and adapted toreceive the lower portion of the cylinder to be etched, said pan havinga protuberance extending longitudinally at one side of the same, adaptedto hold substantially the full amount of mordant to be used at one time,means for swingingly and detachably supporting the pan on the cylinder,and means for swinging the pan to discharge the contents into a sink, orthe like.

HARLEY C. ALGER.

